I wouldn't use an "unstuck" engine without a tear down.

Subject: Re: I wouldn't use an "unstuck" engine without a tear down.

Comments:
: I wouldn't use a previously stuck engine without tearing it down. If it's stuck, then moisture has gotten into the engine via the intake or exhaust valves. You will have rusted/pitted valves, valve stems, valve guides, valve seats, and on cylinder wall above the piston. Without cleaning light surface rust, the rust will jamb into the top piston ring. Moving the piston up and down in the bore will remove most of the rust from the wall, but where did it go? : The problem you will have in addition to the obvious rust is galvanic corrosion. You can see it on the removed piston in the form of a white powdery substance. Any time dissimilar metals are joined with moisture, (ie: aluminum piston and cast iron cylinder walls) you will not only have rust, but galvanic corrosion. This galvanic "cell" is similar to a flashlight battery that uses 2 metals and an acid paste. Another example of galvanic corrosion is in you home water heater. This is why plumbing codes require dielectric unions with metallic pipes and the water heater manufacturer includes a magnesium rod in the water heater's tank to "plate out" and cover the cracks in the glass liner caused by thermo-cycling. : If you free a stuck engine, the galvanic corrosion is going to render the rings immobile and you will have an "oil burner" as Jeff said. : If you have a stuck engine and "unstick" it, then, it's the first step towards a rebuild. I wouldn't place any confidence in an engine that I needed to reliably do work that was stuck and not taken apart and rebuilt. You can use all the magic tricks and potions that you want. You may do this to an engine that you just putter around with, but the seized rings will either burn a lot of oil or will cause excessive wear on the cylinder walls necessitating a rebuld. : I have "unstuck" engines in cars and tractors. I have, also, used previously stuck engines in a race car. In each case, the rings were immobile in the piston grooves which would result with oil burning, compression blow-by, or excessive cylinder wear. Furthermore, I've used engines that weren't stuck, but sat a long time. These had rust jammed in the rings that required rebuilds for reasons aforementioned. : Ken McWilliams : Dayton, Ohio

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